Steel shielded bearings are robust, run easily at higher rotational speeds than rubber sealed bearings and have lower friction naturaly.  They can be prone to water ingress, so should be run with dust shields for long term use on road or off road bikes.  These are the bearings that we use on the Farkham Hall race bikes, without dust seals and they have proved to be perfectly reliable.  Our first choice is always SKF, but where there is no option from that manufacturer, we wil substitute another top quality item from NTN, FAG or NSK.  If you have a preference, please inform  us in the notes for your order.